Air conditioning system



NOV. 14, 1967 c WALTERS 3,352,352

AIR CONDITIONING SYSTEM Filed July 21, 1966 3 Sheets-Sheet 1 ATTORNEY.

Nov; 14, 1967 c. E. WALTERS 3,352,352

AIR CONDITIONING SYSTEM Filed July 21, 1966 5 Sheets-Sheet 2 FIG. 5

INVENTOR. CHARLES E. WALTERS ATTORNEY NOV. 14, c WALTERS AIR CONDITIONING SYSTEM --Sheet 5 5 Sheets il 53 /54 v Filed July 21, 1966 FIG; 9

INVENTOR. CHARLES E. WALTERS ATTORNEY,

United States Patent 3,352,352 AIR CONDITIONING SYSTEM Charles E. Waiters, Birmingham, Ala, assignor of fifty percent to Allen Trask, Utica, NY. Filed July 21, 1966, Ser. No. 566,989 6 Claims. (Cl. 16516) This invention relates to air conditioning systems and particularly to such systems providing automatic control of the heating, cooling, ventilating and humidity within enclosures having high internal heat and humidity gain from occupany by a number of people.

In theaters, restaurants, meeting rooms, school class rooms and the like, there is a substantial internal gain in the air from the heat and water vapor that is given off by the occupants. In restaurants it is common to have heat and water vapor introduced into the air by steam tables, coffee urns, etc. In these and similar enclosures a substantial amount of ventilation is desirable. In school class rooms a minimum amount of outdoor air to be introduced by ventilation is often specified by law as a mandatory requirement in cubic feet per minute per upil. p During the time the air temperature thermostat is calling for either heating or cooling it is desirable in the interest of operating economy to have the ventilation air volume held to the minimum consistent with comfort and to legal requirements where they are in effect. However, during the indoor temperature range wherein the thermostat is satisfied it is desirable to have a high volume of ventilation when the outdoor air does not have excessive humidity, and when the temperature of the outdoor air is cool enough to reduce and/or absorb the internal heat gain within the air conditioned enclosure.

In air conditioning systems it is desirable to have humidity reduction during the time interval of indoor temperature differential set on the thermostat wherein the thermostat is satisfied and therefore holds inoperative the means for heating and the means for cooling the indoor air. Both of these means, when operative, effect humidity reduction, The cooling system does it by condensing water vapor from the recirculated indoor air, and the heating system reduces relative humidity by increasing the water vapor absorbing capacity of the recirculated indoor air by heating it. The conventional air conditioning systems suitable for meeting rooms, school class rooms, small restaurants, and residences do not currently provide for automatic control of ventilation cooling and humidity reduction during the time the air temperature controlling thermostat is satisfied.

In view of the above it is one of the primary objects of the present invention to provide a control system for continuous automatic control of heating, cooling, ventilation, and humidity reduction in an air conditioning system, wherein control of ventilation cooling and humidity continues during the time the heating-cooling thermostat is satisfied.

Another object is increased operating economy of an air conditioning system obtained through an increased differential between a heating-cooling thermostat settings for heating and cooling made practical and consistent with comfort by means for automatic control of ventilation cooling and humidity within the indoor air temperature range of thermostat satisfaction.

Still another object is increased operating economy in an air conditioning system through means for automatically introducing cool outdoor air as it may be required and available during periods of thermostat satisfaction.

Still another object is increased operating economy in an air conditioning system comprising an :air-to-air heat pump for heating and cooling wherein warm ventilation air is discharged into heat exchange relation with the heat pump outdoor coil to reclaim heat therein during heating cycles of the heat pump.

The above and further objects of the present invention will be more apparent from the following detailed description of preferred embodiments thereof, wherein reference is made to the accompanying drawings in the latter of which:

FIG. 1 is a diagrammatic illustration of an air conditioning system embodying the present invention in eluding a split-type air-to-air heat pump with plan views of the heat pump outdoor section, the indoor air handler section with their cabinet top covers removed, and a portion of wall of a structure to be air conditioned with the ventilation openings therein;

FIG. 2 is a diagrammatic side elevation view of the heat pump indoor section of FIG. 1, with a cabinet side panel removed, and a portion of an enclosing structure wall with the openings having ventilation shutters therein taken substantially along line 22 of FIG. 1;

FIG. 3 is a cross-section view of ventilation control means taken substantially along line 3-3 of FIG. 2;

FIG. 4 is an elevation view of the lever adjustment for minimum ventilation associated with the ventilation control means shown in FIG. 3;

FIG. 5 is a side elevation view of door section shown in let associated therewith;

FIG. 6 is a diagrammatic illustration of a plan view of an air conditioning system showing a split type air cooled air conditioner with its indoor evaporator section including a gas furnace for heating, and a portion of wall of the enclosing structure with the ventilation intake air opening therein;

FIG. 7 is a diagrammatic side elevation view of the air conditioning system shown in FIG. 6, with a side panel removed, and a portion of the enclosing structure wall showing the ventilation air inlet shutter for controlling air intake through an opening in the wall taken substantially along line 77 in FIG. 6;

FIG. 8 is a wiring diagram of the air conditioning system shown in FIG. 1 and FIG. 2;

FIG. 9 is a wiring diagram of the air conditioning system shown in FIG. 6 and FIG. 7;

FIG. 10 shows a widely used current model of a heating-cooling thermostat used for controlling indoor temperatures in heat pump installations.

In general, the present invention comprises a control system for conventional air conditioning components to provide heating, cooling ventilation and humidity reduction control, wherein three thermostats and a humidistat together with their control circuits maintain control during the intervals a primary conventional heating-cooling thermostat is satisfied. For heating both a gas furnace and a heat pump, as shown in the drawings, may be used, and for cooling an air conditioner or heat pump, as shown in the drawings, may be used. For the recircu lation of indoor conditioned air, and for ventilation, a conventional blower is used.

When the primary heating-cooling thermostat is calling for heat and the recirculated floor of indoor air is being heated, a predetermined minimum of ventilation is provided through manually adjustable means, and a reduced level of relative humidity is effected by the heating of the air. When the heating-cooling thermostat is calling for mechanical cooling, the heat pump in cooling cycles or the air conditioner, provides cooling of the recirculated air while humidity reduction is effected by the condensation of excess moisture from the indoor air passing through the cooling heat exchanger. During these cooling cycles a predetermined minimum of ventilation the heat pump out- FIG. 1, with a ventilation air out- Patented Nov. 14, 1967' is provided consistent with economy of operating costs, comfort, and, in some instances, legal requirements.

A conventional heating-cooling thermostat usually has a minimum differential between its heating and cooling settings of 4 degrees Fahrenheit wherein the thermostat does notcall for either heating or Cooling and is then said to be satisfied. In the conventional air conditioning systems the control of heating, cooling, and humidity reduction is stopped while the thermostat is satisfied. There is no automatic ventilation control in conventional systems.

In the described embodiments of this invention an automatic control of ventilation, humidity reduction, and sometimes cooling by outdoor air is provided within the satisfaction zone of a primary heating-cooling thermostat. Improved comfort conditions are attained and maintained, and a wider zone of satisfaction, up to 8 degrees for example, may be used for operating economy as well as for improved comfort. In conventional air conditioning systems humidity reduction cannot be effected unless temperature conditions call for either heating or cooling, and it is common to have oppressively high humidity during indoor temperatures which are comfortable when the relative humidity is within the comfort range, and the air conditioner is therefore held inoperative by the satisfaction of the thermostat.

In the present invention the satisfaction of the primary heating-cooling thermostat causes activation of alternate control circuits for temperature, ventilation, and humidity reduction control. A second indoor thermostat set to close on temperature rise of indoor air at a point within the zone of satisfaction of the heating-cooling thermostat increases ventilation to effect cooling by the introduction of cool outdoor air. A third thermostat senses outdoor air temperature and permits the increased ventilation called for cooling when the outdoor air is cool enough to accomplish indoor air temperature reduction.

A humidistat is connected by control circuits to take precedence over increased ventilation within the zone of satisfaction of the heating-cooling thermostat in the event humidity reduction is called for in response to the setting of the humidistat. When the humidistat calls for humidity reduction minimum ventilation is put into effect, and the mechanical cooling system is operated to condense moisture from the air while at the same time an electric heater is energized to reheat the cooled and dehumidified air to a comfort level of temperature within the zone of satisfaction of the primary heating-cooling thermostat.

The following detailed description of two types of air conditioning systems embodying the present invention will more fully set forth the construction, features, and op erating characteristics thereof.

Referring now to FIGS. 1 and 2, the wall of an enclosure to be air conditioned is indicated by the reference numeral 11. Within the wall is an indoor unit of a split type heat pump including a cabinet 12 enclosing a heat exchanger 13, a blower 14, a blower motor 15, and a control panel 16 for enclosing electrical control components and their interconnecting circuits hereinafter described. A ventilation air inlet opening 17 in the Wall 11 is connected to the cabinet 12 with a short duct 18. A ventilation air inlet shutter assembly 19 inside cabinet 12 controls the opening and closing of ventilation air inlet duct 18. An indoor recirculation air shutter assembly 20 controls the flow of recirculated indoor air entering the cabinet 12. Ventilation air exhaust duct 21 in the wall 11 is closed at its indoor end with an automatic shutter 22 arranged to be opened by the pressure of indoor air to be exhausted and closed when required to prevent the entrance of outdoor air therethrough. Supply air duct 23 connected to the outlet of blower 14 delivers air to the air conditioned space through registers such as 24, only one of which is shown in the drawings. An electric heating element 25 is located in duct 23 on the downstream side of blower 14.

An outdoor compressor unit of the reverse cycle refrigerant system shown in FIG. 5 is enclosed in cabinet 26 and includes an outdoor heat exchanger 27, a fan motor 28 and fan 29, a compressor 30, and a cabinet discharge grille 31. The compressor unit assembly is suitably connected to the indoor heat exchanger 13 by refrigerant conduits 32. The heat exchanger 27 is located adjacent the ventilation exhaust duct 21. Fan 29 is adapted to pull air through heat exchanger 27 and exhaust it through grille 31. During cooling cycles cool ventilation air exhausted through duct 21 and drawn through heat exchanger 27, then functioning as a condenser, will reduce condensing pressures and thereby contribute to operating economy. During heating cycles warm ventilation air exhausted through duct 21 and drawn through heat exchanger 27, then functioning as an evaporator, will reclaim heat from the exhaust air and thereby raise evaporating pressure and temperatures to reduce heating cost.

The shutter control motor 33 is shown in FIG. 3 with shutter operating linkage in detail wherein the motor lever 34, attached to the motor shaft, is pivotally connected to transverse link 35. The right hand end of link 35 is pivotally connected to the vertical arm of bell-crank 36 which in turn is pivotally mounted on fulcrum 37. The horizontal arm of bell-crank 36 has a tension spring 38 disposed to hold the recirculation shutter assembly 20' open through connecting link 39 and shutter actuating lever 40. The left hand end of transverse link 35 is pivotally attached to the vertical arm to bell-crank 41 which in turn is pivotally mounted on fulcrum 42. The horizontal arm of bell-crank 41 is connected through a link 43 to the shutter actuating lever 44 of ventilation inlet shutter 19. Through the levers and linkage described shutters 19 and 20 are differentially connected so that the closing of one shutter effects the opening of the other. The two shutter assemblies are shown in FIG. 3 each in the half open position. Motor 33 when energized rotates counterclockwise to open shutter 19 and close shutter 20. When motor 33 is deenergized tension spring 38 opens shutter 20, closes shutter 19, and rotates motor 33 clockwise to the full open position of shutter 20.

At the left hand end of transverse shutter link 35 are five adjustment holes 45 closely spaced and adapted to selectively receive pivot pin 46 for the purpose of ad justing the minimum amount of opening of shutter 19 when shutter 20 is fully open. By the amplitude of opening so adjusted the minimum of outdoor ventilation air drawn in through shutter 19 by blower 14 when shutter 20 is fully opened, is predetermined.

FIGS. 6 and 7 show diagrammatically an air conditioning system fundamentally similar to that shown in FIGS. 1 and 2. In FIGS. 6 and 7 a gas furnace 45 provides heating of the indoor air recirculated therethro-ugh by blower 14, and fin-tube coil heat exchanger 46 of a split type air cooled refrigerant system provides air cooling. Condensing unit 47 is suitably connected to heat exchanger 46 by two refrigerant conduits 48. Air circulation and ventilation is provided and controlled in manner similar to that described in connection with FIGS. 1 and 2.

Referring now to the wiring diagram FIG. 8 the functioning and control of the air conditioning system shown in FIGS. 1 and 2 will be described. Alternating current is supplied to blower motor .15 through manual switch 51 shown closed for continuous air circulation, to compressor motor 52 through the make contact of relay 53, and to the primary winding of transformer 54. The secondary winding of transformer 54 supplies low voltage alternating current to the control components and circuits of the air conditioning system.

The heating and cooling thermostat 55 shown in FIG. 10 has a temperature adjustment lever 49 arranged for setting at the temperature it is desired to have the thermostat call for heat, and lever 50 arranged for setting at the temperature it is desired to have the thermostat call for cooling. Thermostat 55 has cooling contact No. 2 arranged to close on temperature rise at the temperature setting of its adjustment lever 50. Its contact No. 1 is arranged to close one to two degrees in advance of the closing of contact No. 2. The closing of contact No. 1 establishes a circuit from the secondary winding of trans former 54 through conductors 56, 57, 58, the coil of refrigerant circuit reversing valve 60 and conductor 59 to the other side of transformer 54. This circuit operates valve 66 for operation of the refrigerant system in a cooling cycle. When the indoor air temperature rises to the temperature setting of thermostat adjustment lever 50 the thermostat contact No. 2 closes to establish a circuit to relay 61 through conductors 59, 62, 63 and 64. The energizing of relay 61 completes a circuit through conductors 64, 65 and 59 to compressor motor relay 53 which completes the circuit to compressor motor 52 causing it to operate in a cooling cycle.

The air conditioning system continues to operate in a cooling cycle until a temperature lower than the setting of thermostat adjusting lever 50- is reached causing opening of contact No. 2 whereupon compressor 30 is stopped When the indoor air temperature has been reduced to the temperature causing thermostat contact No. 2 to open, relay 61 is deenergized and its back contact then closes to establish a circuit through conductors 56 and 66 to humidistat 67. When humidistat 67 is satisfied its upper contact is closed as shown in FIG. 8 to establish 68 to outdoor thermostat completes a circuit including conductors 56, 59' and 74 to operate shutter motor 33. This closes recirculation shutter 20, and opens ventilation shutter 19 so that the blower 14 will introduce a maximum of cool outdoor air into the air conditioned space.

Thus by this control system a second indoor thermostat 71 will call for cooling on temperature rise before primary thermostat 55 calls for cooling; and if the outdoor air is cool enough to eflect cooling, as sensed by outdoor thermostat 69, then a maximum ventilation capacity is put into operation to continue cooling when thermothen contact No. 2 of thermostat 55 will close to elfect cooling by compressor operation, and the shutter 19 will be returned to minimum ventilation position and shutter 20 to its maximum open position by their linkage spring 38 mg heating cycles and its two heating contacts Nos. 3 and relay 76. Make contact 77 of relay 76 completes a circuit to reversing valve 60 through conductor '80 to hold it in its cooling position; make contact 78 of relay 76 completes a circuit to compressor motor relay 53 through conductors 81 and 65 to operate a compressor 30 in a cooling cycle; and make contact 79 of relay 76 completes a circuit for heater relay 82 through conductors 83, 62, and 59. Relay 82 completes a circuit to one heating element of electric heater 25 with alternating current through its make contact. Humidity reduction is effected by water vapor being condensed from the indoor air as it is recirculated through evaporator 13 by blower 14, and is further reduced by its temperature rise effected by electric heater 25.

When the indoor temperature falls to the temperature setting of adjustment lever 49 of thermostat 55 heating contact No. 3 closes, while the two cooling contacts Nos. 1 and 2 are open. The closing of contact No. 3 energizes relay 61 by completing a circuit through conductors 56, 59, 62, 63 and 64 to the secondary winding of transformer 54. The make contact of relay 61 then completes a cirdetermined by reversing valve 60 being deenergized. The back contact of relay 61 opens to assure deenergizing of relay 73 which in turn deenergizes shutter motor 33 so that shutters 19 and 20 will be returned to their minimum Heating is effected by the reverse indoor air through its functioning as a condenser.

In the event exceptionally cold outdoor temperatures cause the indoor air temperature to fall 1 /2 to 2 degrees below the temperature setting of lever 49 of thermostat 55 contact No. 4 of thermostat 55 closes to complete a circuit to electric heater relay 82 through conductor 84,

mentary heat.

Outdoor thermostat 85 closes on temperature drop and is set to close at an outdoor temperature requiring more heating than can be supplied by the refrigeration system a heating cycle together with the supple- The closing of thermostat 85 completes a circuit extension to relay 86 of the circuit energizing relay 82. Relay 86 in operating completes a circuit to a second element of heater 25 to provide additional supplementary heat. Dura minimum of A review of the an example, follows:

Heating-cooling thermostat 55 has its heating adjustment lever 49 set at degrees to call for heating when the indoor air temperature falls to 70 degrees, and its cooling lever 50 set to call for cooling when the indoor temperature rises to 78 degrees. When thermostat 55 is satisfied its two cooling contacts No. 1 and 2 are open,

4 are open.

Humidistat 67 is set to close its lower contact when the relative humidity of the indoor air rises to 55%. When it is satisfied its upper contact completes a circuit to outdoor thermostat 69 which is set to close at a temperature of 68 degrees. When the contacts of outdoor thermostat 69 are closed it completes a circuit to the second indoor thermostat 71 the contacts of which are adapted to close on temperature rise at 76 degrees to provide maximum ventilation through the operation of shutter motor 33. Thermostat 71 is provided with a differential of approximately 2 degrees so that it will open at approximately 74 degrees to deenergize shutter motor 33 and thereby provide minimum ventilation. Thermostat 71 will control temperature and humidity reduction while the outdoor air provided through the ventilation system is cool enough to prevent an indoor temperature rise to 78 degrees, and dry enough to prevent the indoor relative humidity to rise to 55%. When a call for cooling by thermostat 55 is satisfied, second indoor thermostat 71 will be closed and will continue temperature reduction by maximum circulation of outdoor air when it is 68 degrees or cooler as sensed by outdoor thermostat 69.

When thermostat 55 is satisfied and the relative humidity of the indoor air rises to 55%, then humidistat 67 will take precedence over ventilation and cause shutters 19 and 20 to be set for minimum ventilation and maximum indoor air recirculation. The refrigerant system will be run in a cooling cycle and one element of electric heater 25 will be energized to reheat the cooled and dehumidified air.

When the indoor air temperature falls to 70 degrees, heating contact No. 3 of thermostat 55 will close to operate the refrigerant system in a heating cycle. If the refrigerant system cannot maintain the 70 degree temperature called for, and the indoor air temperature falls to 68 degrees, contact No. 4 will close to turn on the first element of heater 25 through the closing of heater relay 82. If the outdoor temperature is so cold that the operating of the refrigerant system in a heating cycle together with the supplementary heat of one element of heater 25 does not provide the necessary heat, then outdoor thermostat 85 will close to bring on the second element of heater 25, through its actuating heater relay 86, to provide additional supplementary electric heat.

Referring now to the wiring diagram FIG. 9 the functioning and control of the air conditioning system shown in FIGS. 6 and 7 will be described.

Alternating current is supplied to blower motor 15 through a manual switch 51 shown closed, to compressor motor 52 through the make contact of relay 53, and to the primary winding of transformer 54. The secondary winding of transformer 54 supplies low voltage alternating current to the control components and circuits of the air conditioning system. Blower 14, driven by motor 15 circulates indoor and ventilation air continuously through supply duct 23, and registers 24.

The heating-cooling thermostat 87 similar to thermostat 55 shown in FIG. 10 has temperature adjustment lever 49 arranged for setting at the temperature it is desired to have the thermostat call for heat, and lever 50 arranged for setting at the temperature it is desired to have the thermostat call for cooling. Thermostat 87 has a cooling contact No. 1 arranged to close on temperature rise at the temperature setting of its adjustment lever 50, and its heating contact No. 2 arranged to close on temperature drop at the temperature setting of its adjustment lever 49. When the indoor temperature rises to the setting of adjustment lever 50 the thermostat contact No. 1 closes to establish a circuit to relay 61 through conductors 56, 91, 92 and 59. The energizing of relay 61 closes its make contact to complete a circuit through conductors 91, 65 and 59 to compressor motor relay 53 which through its make contact completes a circuit for operation of compressor motor 52 in a cooling cycle.

When the indoor air temperature has been reduced to the temperature causing thermostat 87 contact No. 1 to open, relay 61 is deenergized and its back contact closes to establish a circuit through conductors 56 and 66 to humidistat 67. When humidistat 67 is satisfied its upper contactis closed as shown in FIG. 9 to establish a circuit through conductor 68 to outdoor thermostat 69. Outdoor thermostat 69 closes on temperature drop and may be set to close at a temperature equal to or colder than the temperature setting of thermostat 87 which calls for heating. When thermostat 69 is closed the above circuit is continued through conductor 70 to second indoor thermostat '71. Thermostat 71 is arranged to close on temperature rise and is set to close at a temperature approximately two degrees lower than the temperature setting of adjustment lever 50 of thermostat 87. When both outdoor thermostat 69 and indoor thermostat 71 are closed the above circuit is extended through conductors 72 and 59 to energize shutter motor relay 73. Relay 73 completes a circuit to shutter motor 33 through conductors 56, 59 and 74 to close recirculation shutter 20, and open ventilation shutter 19 so that blower 14 will introduced a maximum of cool outdoor air into the air conditioned space.

Thus by this control system similar to that of FIG. 8, a second indoor thermostat 71 will call for cooling on temperature rise before primary thermostat 87 calls for cooling; and if the outdoor air is cool enough to effect cooling, as sensed by outdoor thermostat 69, then a maximum ventilation capacity is put into operation to effect cooling, or to continue cooling, where thermostat 87 is satisfied. If the outdoor air is not cool enough to keep thermostat 87 satisfied, or the indoor heat gain is too high to be absorbed by the ventilation air available, then contact No. 1 of thermostat 87 will close to effect cooling by compressor operation, and the shutters 19 and 20 will be returned to minimum ventilation positions by their linkage spring 38.

When thermostat 87 is satisfied and humidistat 67 calls for humidity reduction, relay 73 is deenergized to open the circuit to shutter motor 33 whereupon linkage spring 38 returns shutters 19 and 20 to their minimum ventilation position. The closing of humidistat contact 75 completes a circuit to energize relay 89 through conductors 56, 66, 92 and 59. Relay 89 in operating completes circuits for operation of compressor motor relay 53 through contact 93 and conductors 81, 65 and 59 to operate compressor 30 in a cooling cycle; and through make contact 94 to energize heater relay through conductors 95, 92 and 59 to supply electric heater 25 with alternating current. Humidity reduction is effected by water vapor being condensed from the indoor air as it is'recirculated by blower 14, and is further reduced by its temperature rise elfected by electric heater 25 downstream of refrigerant heat exchanger 46.

When the indoor temperature falls to the temperature setting of adjustment lever 49 of thermostat 87 then heating contact No. 2 closes, and cooling contact No. 1 remains open. The second indoor thermostat 71 is 'arranged to open at a temperature above the setting of thermostat 87 adjusting lever 49 to release relay 73 which in turn deenergizes shutter motor 33 and permits the return of shutters 19 and 20 to their minimum ventilation position. The closing of heating contact No. 2 completes a circuit to open gas valve 88 through conductors 56, 96, 92 and 59 to start operation of gas furnace 45. Indoor air and ventilation air circulated by blower 14 through gas furnace 45, heat exchanger 46, supply duct 23 and register 24 will be heated by gas furnace 45 during the time thermostat 87 calls for heating.

A review of the air conditioning control system functioning according to the control system of FIG. 9, using specific thermostat closing and opening temperatures as an example, follows:

Heating-cooling thermostat 87 has its heating adjustment lever 49 set at 70 degrees to call for heating when the indoor air temperature falls to 70 degrees, and its cooling lever 50 set to call for cooling when the indoor temperature rises to 78 degrees. When thermostat 87 is satisfied its two contacts, No. 1 and No. 2, are open.

- mum indoor air recirculation by the Humidistat 67 is set to close its lower or make contact 75 when the relative humidity of the indoor air rises to 55%. When it is satisfied its back or upper contact completes a circuit to outdoor thermostat 69 which is set to close on temperature drop to 68 degrees. When the outdoor thermostat 69 is closed it completes a circuit to the second indoor thermostat 71 which is set to close on temperature rise at 76 degrees to provide maximum ventilation through the opertaion of shutter motor 33. Thermostat 71 is provided with a differential of approximately two degrees so that it will open at 74 degrees to deenergize shutter motor 33 and thereby provide minimum ventilation. Thermostat 71 will control temperature and humidity reduction while the outdoor air provided through the ventilation system is cool enough to prevent an indoor temperature rise to 78 degrees, and dry enough to prevent the indoor relative humidity to rise to 55%. When a call for cooling by thermostat 87 is satisfied, second indoor thermostat 71 will be closed and will continue temperature reduction by maximum circulation of outdoor air when it is 68 degrees or cooler as sensed by outdoor thermostat 69.

When thermostat 87 is satisfied and the relative humidity of the indoor air rises to 55%, then humidistat 67 will take precedence over ventilation and cause shutters 19 and 20 to be set for minimum ventilation and maxirelease of relay 73. The refrigerant system will be run in a cooling cycle and electric heater 25 will be energized to reheat the cooled and dehumidified air.

When the indoor air temperature falls to 70 degrees, heating contact No. 2 of thermostat 87 will close to operate gas furnace 45 intermittently or constantly as may be required to maintain the indoor air temperature at approximately 70 degrees during the time outdoor temperatures are lower than 70 degrees.

While this invention has been shown in but two embodiments thereof, it will be obvious that various modifications may be made therein without departing from the spirit or essential attributes thereof, and it is desired therefore that only such limitations be placed thereon as are specifically set forth in the appended claims.

What is claimed is:

1. In an air conditioning system for an enclosed structure, said system including means for cooling, means for re-circulating, means for ventilating, and means for heating the air within said structure, control circuits for said means including, a first thermostat sensing air temperature within said structure, said thermostat having a first setting means for controlling said heating circuit means does not call for either heating or cooling, a second thermostat sensing air temperature within said structure having its setting within the said satisfaction temperature its control circuit and set to close on temperature drop at a temperature less than the setting of said second thermostat whereby cooling may be effected by the call of said second thermostat where outdoor air temperature is lower than the indoor temperature.

2. In an air conditioning system for an enclosed structure, said system including means for cooling, means for recirculating, means for ventilating, and means for heating the air within said structure, a first thermostat sensing air temperature within said structure having a first setting means for controlling heating and a second setting means for controlling cooling arranged for the setting of a differential range of satisfaction therebetween wherein said firstthermostat does not call for either heating or cooling, a second thermostat sensing air temperature within said structure having its setting within the said temperature range of satisfaction of said first thermostat and arranged to call for increased ventilation by said ventilation means in response to temperature rise, and a third thermostat sensing outdoor air temperature arranged and set to permit increased ventilation called for by said second thermostat only when the outdoor air temperature is less than the setting of said second thermostat, and a humidistat sensing indoor air arranged to take precedence over a call for ventilation by said second thermostat when calling for humidity reduction and to effect humidity reduction by causing operation of said cooling means.

3. In an air conditioning system for an enclosed structure, said system including means for cooling, means for recirculating, means for ventilating, and a primary means for heating the air within said structure, a first thermostat sensing air temperature within said structure having a first setting means for controlling heating and a second setting means for controlling cooling arranged for the setting of a differential range of satisfaction therebetween wherein said first thermostat does not call for either heating or cooling, a second thermostat sensing air temperature within said structure having its setting within the said temperature range of satisfaction of said first thermostat and arranged to call for increased ventilation by said ventilation means in response to temperature rise, a third thermostat sensing outdoor air temperature arranged and set to permit increased ventilation called for by said second thermostat only when the outdoor air temperature is less than the setting of said second thermostat, said means for air recirculation including a blower and secondary air heating means downstream of said primary heating means, and a humidistat sensing indoor air relative humidity arranged to take precedence over a call for ventilation by said second thermostat when calling for humidity reduction and to effect humidity reduction by causing operation of said cooling means together with said secondary heating means to reheat air cooled and dehumidified by said cooling means.

4. In an air conditioning system for an enclosed structure, said system including heat pump means for heating and cooling, means for recirculating and a means for ventilating the air within said structure, a first thermostat sensing air temperature within said structure having a first setting means for controlling heating and a second setting means for controlling cooling arranged for the set ting of a differential range of satisfaction therebetween wherein said first thermostat does not call for either heating or cooling, a second thermostat sensing air temperature within said structure having its setting within the said temperature range of satisfaction of said first thermostat and arranged to call for increased ventilation means in response to temperature rise, a third thermostat sensing outdoor air temperature arranged and set to permit increased ventilation called for by said second thermostat only when the outdoor air temperature is less than the setting of said second thermostat, said means for air re-circulation including a blower and secondary air heating means downstream of said heat pump means, and a humidistat sensing indoor air relative humidity arranged to take precedence over all for ventilation by said second thermostat when calling for humidity reduction and to effect humidity reduction by operation of said heat pump means in a cooling cycle together with said secondary heating means to reheat air cooled and dehumidified by said heat pump means.

5. In an air conditioning system for an enclosed structure, said system including a condensing unit and evaporator means for cooling, means for recirculating, means for ventilating, and furnace means for heating the air within said structure, a first thermostat sensing air temperature within said structure having a first setting means for controlling heating and a second setting means for controlling cooling arranged for the setting of a diiferen tial range of satisfaction therebetween wherein said first thermostat does not call for either heating or cooling, a second thermostat sensing air temperature within said structure having its setting within the said temperature range of satisfaction of said first thermostat and arranged to call for increased ventilation by said ventilation means in response to temperature rise, a third thermostat sensing outdoor air temperature arranged and set to permit increased ventilation called for by said second thermostat only when the outdo-or temperature is less than the setting of said second thermostat, said means for air recirculation including a blower and secondary air heating means downstream of said furnace means, and a humidistat sensing indoor air arranged to take precedence over call for ventilation by said second thermostat when calling for humidity reduction and to effect humidity reduction by causing operation of said condensing unit and evaporator means together with said secondary heating means to reheat air cooled and dehumidified by said condensing unit and evaporator means.

6. In an air conditioning system for an enclosed structure, said system including means for cooling, means for re-circulating, means for ventilating, and means for heating the air within said structure, control circuits for said means, said control circuits including a first and a second thermostat for sensing air temperatures within said structure, and a third thermostat for sensing air temperatures outside of said structure cooperating with said second thermostat, said first thermostat having a first temperatu're setting below which said circuits are conditioned to operate said heating means and a second higher temperature setting above which said circuits are conditioned to operate said cooling means, said second thermostat having a temperature setting between the settings of said first thermostat above which said circuits are conditioned to operate said ventilating means to a first degree and below which said circuits are conditioned to operate said ventilating means to a second degree, said third thermostat having a temperature setting below the temperature setting of said second thermostat below which lower setting said second thermostat is conditioned to operate said ventilating means to a first degree and above which said circuits are conditioned to operate said ventilating means to a second degree.

References Cited UNITED STATES PATENTS 2,209,787 7/ 1940 Miller 165-16 2,372,839 4/1945 McGrath 165l6 ROBERT A. OLEARY, Primary Examiner.

C. SUKALO, Assistant Examiner. 

1. IN AN AIR CONDITIONING SYSTEM FOR AN ENCLOSED STRUCTURE, SAID SYSTEM INCLUDING MEANS FOR COOLING, MEANS FOR RE-CIRCULATING, MEANS FOR VENTILATING, AND MEANS FOR HEATING THE AIR WITHIN SAID STRUCTURE, CONTROL CIRCUITS FOR SAID MEANS INCLUDING, A FIRST THERMOSTAT SENSING AIR TEMPERATURE WITHIN SAID STRUCTURE, SAID THERMOSTAT HAVING A FIRST SETTING MEANS FOR CONTROLLING SAID HEATING CIRCUIT MEANS AND A SECOND SETTING MEANS FOR CONTROLLING SAID COOLING CIRCUIT MEANS ARRANGED FOR THE SETTING OF A TEMPERATURE SATISFACTION RANGE BETWEEN WHICH SAID FIRST THEREMOSTAT DOES NOT CALL FOR EITHER HEATING OR COOLING, A SECOND THERMOSTAT SENSING AIR TEMPERATURE WITHIN SAID STRUCTURE HAVING ITS SETTING WITHIN THE SAID SATISFACTION TEMPERATURE RANGE OF SAID FIRST THERMOSTAT, SAID SECOND THERMOSTAT BEING ARRANGED TO CONTROL SAID CIRCUITS TO OPERATE SAID VENTILATION MEANS IN RESPONSE TO A TEMPERATURE RISE ABOVE ITS SETTING, AND A THIRD THERMOSTAT SENSING OUTDOOR AIR TEMPERATURE COOPERATING WITH SAID SECOND THERMOSTAT IN ITS CONTROL CIRCUIT AND SET TO CLOSE ON TEMPERATURE DROP AT A TEMPERATURE LESS THAN THE SETTING OF SAID SECOND THERMOSTAT WHEREBY COOLING MAY BE EFFECTED BY THE CALL OF SAID SECOND THERMOSTAT WHERE OUTDOOR AIR TEMPERATURE IS LOWER THAN THE INDOOR TEMPERATURE. 